How Will IPv6 Impact your Network?

painlosososSoftware and s/w Development

Jun 30, 2012 (5 years and 2 months ago)


The transition to IPv6 protocol is officially under way. The global
top-level repository of IPv4 addresses expired, and just a few
quickly dwindling pools of addresses remain at the world’s five
regional Internet registries.
Going forward, your network will have to accommodate a growing
population of IPv6-enabled devices: new equipment is shipping with
IPv6 simply because there are so few unused IPv4 addresses left.
The American Registry for Internet Numbers (ARIN), one of the
remaining registries suggests that all Internet servers be prepared
to serve IPv6-only clients by January 2012. And in September 2010,
the U.S. Obama administration issued a directive requiring all U.S.
government agencies to upgrade their public-facing Web sites and
services to support native IPv6 by September 30, 2012.
Start with the Internet
As these deadlines suggest, the first place that the IPv6 transition
will affect your network is in the public Internet segment. You’ll want
to upgrade your Web-facing content and mail servers to IPv6 first so
all users can access content on your Web site, regardless of which
network protocol their devices support. Otherwise, there might be
some mismatches and lack of interoperability between Web resources
and users.
Newer IPv6-only mobile devices, for example, might not be able to
locate IPv4 Web sites. Similarly, e-commerce sites that run only IPv4
or IPv6 (not both) might be unable to receive orders from user access
devices running the protocol that the site doesn’t support.
Dual Stack Interoperability Approach
Preparing equipment to “speak” either protocol involves using a
standard dual-stack IP addressing approach to IP interoperability.
Running this implementation in the operating system of network
equipment, servers and client devices enables network infrastructure
components to communicate with either IPv4 hosts or IPv6 hosts in
their native language.
Some newer industries may run only IPv6 from the start. Consider
a utility company monitoring IP-enabled smart meters or a home-
appliance company monitoring and servicing IP-enabled refrigerators,
washers, dryers and other equipment over the network. These
enterprises will probably need to communicate with these remote
devices, machine to machine, using IPv6. That’s because the
forthcoming avalanche of IP-enabled smart home devices and sensors
will be assigned only IPv6 addresses.
The transitional issues associated with enabling millions of existing
IPv4-based devices to communicate with IPv6 Web sites and devices
(and vice versa) mean that dual-stack IP addressing will need to be in
place for a long time.
Another interoperability approach that can be deployed among
components in the enterprise private WAN is tunneling. Tunneling is
used in exceptional cases where running dual-stack IP software isn’t
feasible, such as on older equipment. It involves encapsulating IPv6
packets within IPv4 so that two islands of IPv6 can interconnect using
an IPv4 network in the middle.
Figuring out what network elements are candidates for each type of
transition requires a well-thought-out planning process (see figure on
top of page 2).
How Will IPv6 Impact your Network?
Fast Fact
In 1995, the Institute of Electrical and Electronic Engineers
(IEEE) global standards body specified a whole new Internet
Protocol, called IPv6, which adds several services to the protocol
and lengthens the address space from 32 bits to 128 bits. The
greater address space means there are many, many more possible
combinations of bits, resulting in an almost an infinite number of
IPv6 addresses.
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The Diminishing Role of Network Address Translation (NAT)
In the short term, your private WAN could see fewer effects of the
transition to IPv6 if you currently use Network Address Translation
(NAT) to conserve internal IPv4 addresses. But in general, NAT’s days
are numbered, both at the enterprise edge and particularly in service
provider networks.
Enterprise NAT
IP identifies a network or client device by an address – either a
globally unique one or a reusable one assigned temporarily from a pool
of addresses from a Dynamic Host Control Protocol (DHCP) server. NAT
is a longtime practice in IP networking to conserve IPv4 addresses and
add a measure of security to private enterprise networks.
NAT aggregates multiple, non-exclusive IP addresses behind the
corporate WAN router, but shows just one unique address on the
router interface to the public Internet. In other words, multiple
enterprises’ private IP networks could be using the same IPv4 address
ranges internally, but the NAT router facing the public Internet displays
a unique IP address that is globally routable.
Typically, the local enterprise WAN edge IP router uses NAT to keep
track of who’s who behind the WAN edge and maps end points to one
another accordingly. Once a “hidden” device behind the NAT-enabled
router establishes a session, the NAT device keeps stateful information
about the session and thus “remembers” who at the back end is
connected to whom or what in the public Internet.
In this way, NAT has been the conservator of IP addresses that bought
the industry many years of time before having to migrate to IPv6’s
longer addressing scheme. However, the hidden aspect of individual
resource IP addresses will not survive long in the more peer-to-peer
oriented architectures of private and public networks (see below)
going forward.
Cloud-based NAT: A Temporary Fix
NAT can also be used in the service provider network in the form
of Large Scale NAT, or LSN. LSN moves today’s NAT mapping and
translation functions from the edge of enterprise and home networks
into the service provider’s network, creating a “centralized NAT.”
This effort involves the service provider doing
what enterprises have been doing with NAT in
their private networks but on a much larger
scale: masking thousands of customers behind
a single IPv4 address. The temporary benefit
of this is that it stretches a service provider’s
public IPv4 address space and buys time before
wholesale IPv6 upgrades must occur.
There are serious drawbacks to this approach, however. For example,
identifying individual devices and users behind the NAT becomes
quite difficult. That’s because when using LSN, each address no longer
represents a single machine, residence or office. That IPv4 address
now represents thousands of machines and users belonging to
multiple service provider customers behind the NAT-enabled routers.
So it becomes quite challenging to continue to map sessions and track
who’s who, and some connections are likely to break.
For example, applications with “push” sessions – those that are
initiated by another party and intended to reach a given user – aren’t
possible, because the subscriber is hidden behind an IPv4 address that
makes his or her specific address unidentifiable. While on an enterprise
scale a router can retain stateful information about the two ends of
a session and map flows to the proper end points accordingly. This
becomes quite complex – in fact, nearly impossible – when the service
How Will IPv6 Impact your Network?
Fast Fact
The main driver to the new IPv6 protocol is that the IPv4 address
space is virtually depleted. But IPv6 also offers new services and
• Built-in support for IPsec encryption
• Autoconfiguration, enabling systems to gain a network address
without administrator intervention
• More classes of service, so potentially higher quality of service
(QoS) and improved service-level agreements (SLAs)
Program Governance
and Communication
• Create IPv6 transition
timelines, sequencing
and interdependencies
• Identify governance
team to oversee plan
• Develop review and program
management aspects of
overall plan, timelines and
assigned transition teams
• Execute plan
Strategy and ArchitectureInfrastructure Readiness
• Quantify infrastructure readiness
and understand transition impacts
• Categorize Components for Readiness
• Research IPv6 technologies utilized for
transition (tunnels, translation mechanisms)
• Develop IP Addressing Plan
• Develop a thorough transition strategy
Testing and PilotingDesign and Engineering
• Develop detailed design and equipment
configurations, including:
— IP addressing
• Identify and assign transition sequencing
and engineering tasks
• Create IPv6 test labs
• Develop test plans and production piloting
• Conduct dual stack testing
• Tunneling
Planning Process for IPv6
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provider has no routing knowledge of each customer’s private, internal
IP network.
In addition, some Web site owners and Internet service providers (ISPs)
block access based on IP address because of bad behavior of a single
machine, user or network. But if thousands of customers and devices
are behind one IP address, blocking access from it could unjustifiably
deny service to many other customers of that provider.
These are some of the reasons that LSN should be considered a
transitional and temporary approach to implementing IPv6, rather
than a substitute for it.
Ultimately, pushing IPv6 as close to end users
as possible – within individual enterprises and
residences – avoids the additional layers of
mapping and conversion that take place going
through at least one large-scale layer of NAT
and possibly another at the enterprise edge.
Those conversions slow down performance
and can break connections.
Benefits, Cautions with IPv6 Internet Connections
Direct IPv6 connections to the Internet bring both benefits and new
challenges. For example, direct connections could actually improve
peer-to-peer communications, such as voice over IP (VoIP). On the
other hand, they introduce some new security risks.
VoIP Could Get Easier
An inherent benefit of IPv6 is that it delivers on the true intent of an
IP network, namely bi-directional communication where end-point
addresses are known by both parties. The arrival of IPv6 should
eventually enhance VoIP when NAT functions disappear from the
picture. Today, NAT makes it impossible to set up Session Initiation
Protocol (SIP)-based calls to devices with private IP addresses unless
the initiating VoIP device finds a way to bypass a firewall to get inside
and find an intended recipient’s IP address in the company’s server.
Because VoIP sessions are inherently peer-to-peer in nature, this could
be a reason to prioritize opening up the internal SIP service with a
globally unique IPv6 address first, particularly if you are planning to
eventually move away from NAT. Getting rid of NAT, inevitable though
it may be, has implications for your security infrastructure.
Security/VPN Impact
When NAT ultimately disappears from the edge of the enterprise
network, individual IPv6 addresses will be exposed directly to the
public Internet. IPv6 does require support for IPsec as a fundamental
interoperability requirement, indicating that it will be inherently more
secure than IPv4. In other words, an IPsec VPN is built directly into the
IPv6 network.
If you are an enterprise using a Multi-Protocol Label Switching (MPLS
VPN) service, there should be no effect of IPv6 joining the network
given that MPLS is a different protocol altogether. Whether you
are running IPv4 or IPv6, the protocol will be encapsulated in an
MPLS “wrapper.”
Service providers, on the other hand, need to support IPv6 in the
routers at the edge of their networks (the provider edge, or PE,
routers) in the form of dual-stack IPv4/IPv6.
Note, though, that because IPv6 isn’t backward compatible with IPv4,
you’ll need to upgrade some existing security tools to speak IPv6,
basically recreating the security infrastructure you have in place for
your IPv4 networks for the newer version of the protocol.
According to the National Institute of Standards and Technology (NIST):
Prevention of unauthorized access to IPv6 networks will likely be
more difficult in the early years of IPv6 deployments. IPv6 adds more
components to be filtered than IPv4, such as extension headers,
multicast addressing, and increased use of ICMP. These extended
capabilities of IPv6, as well as the possibility of an IPv6 host
having a number of global IPv6 addresses, potentially provides an
environment that will make network-level access easier for attackers
due to improper deployment of IPv6 access controls. Moreover,
security related tools and accepted best practices have been slow
to accommodate IPv6. Either these items do not exist or have not
been stress tested in an IPv6 environment. Nevertheless, global
aggregation of IPv6 addresses by ISPs should allow enhanced anti-
spoofing filtering across the Internet where implemented
Transition to IPv6 Summary: 5 Steps
When you move away from NAT, you’ll need to support IPv6 on your
internal network. For that to happen, you’ll need a comprehensive
strategy and detailed planning process that enables you to migrate
using the following steps:
1. Establish an IPv6 Internet presence.
This involves adding IPv6 to your public servers. First, enable your
public-facing Web and email servers with an IPv6 address in addition
to their IPv4 addresses. This makes more resources available via IPv6
for everyone.
2. Enable internal users to access IPv6-enabled sites on the Internet.
This involves upgrading their operating systems to dual-stack
addresses, if it hasn’t already happened automatically by your OS
system provider.
3. Migrate your WAN to dual stack (supporting both IPv4 and
IPv6 protocols) by upgrading your WAN access routers.
This allows your private enterprise network to interoperate with
newer networks and resources that support only IPv6 due to lack
of IPv4 addresses.
4. Determine select priority migration candidates from there.
Consider whether you want to migrate any piece of your internal
network out to the public IPv6 network – in other words, are there
devices or subnetworks that could interface directly to the Internet?
As mentioned, your VoIP and unified communications environment
might be an early candidate, because of the peer-to-peer nature of it.
As you introduce IPv6, remember that your DHCP servers will need an
upgrade so they can assign IPv6 addresses.
How Will IPv6 Impact your Network?
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5. Plan ahead for the long term
Over the long haul, you should plan to migrate your entire network
to IPv6 and phase out NAT entirely. The main reason is simply that
everything will need to be IPv6 sooner or later. Also, the mix of devices
and connections likely to join your network, such as Wi-Fi-enabled
smart phones and consumer-grade devices phones and tablets tend to
change frequently, making it difficult for NAT to keep track of them and
the state of their sessions.
Consider, too, that other machines that might one day connect to your
IP network: soda machines, thermostats, surveillance cameras and
other facilities aspects of the building, for example. Again, if you have
NAT in place, getting to these individual devices becomes complex if
NAT has to have some way to identify all of them and map application
flows accordingly.
1. Guidelines for the Secure Deployment of IPv6 (Draft):
Recommendations of the National Institute of Standards and
Technology, February 2010.
For more information on how AT&T can help you prepare and implement your transition strategy,
How Will IPv6 Impact your Network?
05/04/12 AB-2234
© 2012 AT&T Intellectual Property. All rights reserved. AT&T and the AT&T logo are trademarks of AT&T Intellectual Property.
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